Chemistry help!

Question

The following equilibrium

N₂O_4(g)   D   2NO_2(g)

has an equilibrium constant Kc = 0.20 at some temperature. Calculate the concentration of N₂O₄ in mol/L if the concetration of NO₂ is found to be 0.32 M.

Answer 1

N₂O₄ <==> 2NO₂ ... balanced chemical equation

Kc = 0.20 = [NO₂]²/[N₂O₄] = (0.32)²/[N₂O₄]

[N₂O₄] = (0.32)²/(0.20) = 0.1024/0.20 = 0.512 = 0.51 mol/L